TESTING MILK 

FOR 

BUTTER FAT 

BY 
THE BABCOCK TEST 




DISTRIBUTED BY 
BORDEN'S CONDENSED MILK CO. 



TESTING MILK 

FOR 

BUTTER FAT 

BY 
THE BABCOCK TEST 



Compiled by 

W. E. E VA N S 

Neffsville, Pa. 



Copyright, 19 17, b 
W. E.EVANS 



SF253 



AN APPRECIATION. 

"By means of the Babcock test, dairying has been 
developed from one of the most haphazard of indus- 
tries to an exact and attractive business enterprise. 
The Babcock test has been so intimately connected 
with and largely responsible for the progress in dairy- 
ing not only in this state but throughout the country 
and the world, that proficiency in its use has become 
almost synonymous with better cows, better milk and 
better farming. 

"It has served as the necessary stimulant to raise 
dairying from a disliked side line to a profession 
worthy of the efforts of well trained men. It has 
made dairymen honest, has placed dairying on a 
scientific basis, has promoted factory efficiency and has 
stimulated the breeding up of productive herds. 

"The Babcock test has struck the shackles which 
bound dairy farmers to past traditions, and has 
started them on their way to greater prosperity." 

H. L. Russell, 

Director. 
Wisconsin Experiment Station. 



©CI.A472567 

2 

AUG 10 1917 



CONTENTS 



Page 

Introduction 5 

Theory of the Test 5 

Apparatus 5 

Getting an Accurate Sample 6 

Preserving Samples 6 

Performing the Test 6 

Uniform Temperature 6 

Mixing the Milk 7 

Measuring the Milk 7 

Transferring Milk to Test Bottles 9 

Adding the Acid 9 

Mixing Acid and Milk 10 

Whirling ■ 10 

Tempering the Tests 11 

Reading the Tests 11 

Causes of Poor Tests 11 

Variations of Butter Fat 13 



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Fig. 1 

Milk Testing Bottles 



The eight per cent, bottle is graduated to tenths while the ten per 
cent, bottle is graduated to fifths. The use of the eight per cent, bottle 
is specified by the Official Dairy Instructors' Association, and as it 
makes possible more accurate readings, is used by many licensed 
testers. It also conforms to the requirements of the U. S. Bureau of 
Standards. 

4 



THE BABCOCK TEST FOR FAT IN MILK 



INTRODUCTION. 

SO many inquiries are made about the Babcock Test for Fat in 
Milk it would appear that the subject is not yet fully understood 
by all. Many seem to think that the Babcock Test is a compli- 
cated process and at best unreliable. This is an erroneous idea. The 
test is simple, accurate and easily mastered by any one who will give 
the matter careful study and attention. 

THEORY OF THE TEST. 

Owing to the lightness of the fat globules they tend to rise to the 
surface to form a layer of cream, but because of the other solids in the 
milk, the fat globules do not all succeed in getting to the top. It was 
found that sulphuric acid would dissolve the other milk solids without 
affecting the fat globules and would thus permit them to rise to the top 
more readily. 

Just as a wagon wheel throws the mud from the tires when the 
horses are going rapidly, so by whirling the milk and sulphuric acid 
at a high rate of speed the fat will be separated quickly, as well as 
effectively. Dr. S. M. Babcock, of the University of Wisconsin, in 
1890, was the first to furnish a practical means of using these facts. 
This method, called the Babcock Test, was given to the world as a 
free scientific discovery and is now in general use for determining the 
percentage of butter fat in milk. (It is interesting to note that the 
Legislature of Wisconsin in 1899 presented Dr. Babcock with a large 
gold medal recognizing "the great value to the state and to the whole 
world of the invention and discovery.") 

APPARATUS. 

The apparatus used in making the test is as follows: 

a. Milk Pipette (capacity 17.6 c.c). 

b. Babcock Milk Test Bottles. 

c. Acid Measure (capacity 17.5 c.c). 

d. A Small Dipper for Taking Sample. 

e. A Pair of Dividers. 

f. A Centrifugal Machine to Whirl the Bottles. 

g. A Water Bath to Maintain Correct Reading Temperature, 
h. Thermometer. 

j. Pint Fruit Jar. 

k. Acid Testing Hydrometer. 

5 



GETTING AN ACCURATE SAMPLE. 

After the cow's milk has been thoroughly mixed by being poured 
from one vessel to another three or four times, the sample is taken 
either with a small dipper or a regular sampling tube or "milk thief." 
An accurate sample cannot be taken with an ordinary drinking 
or tea cup. The accuracy and value of the test depend largely on 
the care exercised in taking the sample. When we bear in mind, 
first, that the first part of the cow's milk is very poor 
in butter fat and the last part or strippings very rich 
in fat; second, that the percentage of butter fat in 
the morning's and night's milk frequently varies, it 
is self evident that a composite sample consisting of 
a number of small samples from different milkings 
gives a more accurate estimate of the cow's test. A 
representative sample is the first and most important 
item and, as a sample from a single milking will not 
give an average or representative test, it must be 
taken from a number of both morning and night 
milkings. The several small samples which go to 
make up a composite sample should be proportional 
in quantity; that is, if a cow gave 18 pounds in the 
morning and 12 pounds in the evening milking, the 
sample from the morning milking should be one and 
one-half times as large as the sample taken from the 
evening milking. 

PRESERVING SAMPLES. 

In order to keep samples of milk any length of 
time some preservative such as corrosive sublimate 
must be added and the milk must be kept in air 
tight bottles (an ordinary pint fruit jar is excellent), 
and if the weather is very warm the jars of milk 
samples must be stored in a cool place. (Corrosive 
sublimate is sold in tablet form by druggists.) If 
the milk samples become sour and contain lumps 
of curd add a knife point of soda lye ; shake and let 
it stand until the curd is thoroughly dissolved. 
When this is done the sulphuric acid should be added a little at 
a time as the chemical action is violent. 



Fig. 2 

Dipper for taking 
samples 



PERFORMING THE TEST. 

Uniform Temperature. — The milk to be tested and the acid to 
be used should have a uniform temperature of from 60 to 70 degrees, 

6 



Fahr. If either the acid or the milk to be tested are much higher 
than 70 degrees the fat column will be dark and contain charred 
matter and thus spoil the accuracy of the test. 

Mixing the Sample. — The sample to be tested must be thor- 
oughly mixed by shaking vigorously and by pouring from one vessel 
to another. 

If the sample is a composite sample of milk delivered each day it 
is very essential that the jar of milk is shaken each time before a 
new sample is added and particularly so afterward, so as to be sure 
that the new sample is incorporated with the old ones. In order to 
obtain a homogeneous mixture it is sometimes necessary to warm 
composite samples to 85 degrees, Fahr., or even as high as 110 degrees 
if necessary by placing the jar in a water bath of the desired tempera- 
ture, but it is absolutely necessary to reduce this temperature again 
to 60 or 70 degrees, Fahr., before drawing the sample into the pipette 
if a correct test is to be made. 

If any cream adheres to the inside of the jar it is due to neglect 
of proper shaking each day or storage in a warm place or an un- 
cleanly jar, and under no circumstances may this cream be taken off 
of the inside of the jar with a test tube brush because this cream 
will simply adhere to the bristles of the brush and a low test will 
result. 

Measuring the Milk. — The instrument used to measure the milk 
for the test is called a pipette. There are two kinds of pipettes in 
common use, the "up-to-date" and the common pipette. (See illus- 
trations.) The common pipette is just as accurate as the "up-to- 
date" pipette, if properly handled; and is less cumbersome, and if 
many samples are to be tested it is the quicker method of taking the 
sample. It has only one mark on the neck and when filled to this 
mark (see Fig. 3) holds 17.6 cubic centimeters of milk. 

Place the narrow tip of the pipette into the milk while it is still 
in motion and with the mouth suck the air out until the milk rises 
in the pipette above the mark on the neck. Quickly place the index 
finger over the upper end of the pipette before the milk runs below 
the mark. By cautiously releasing the finger, the column of milk 
can be lowered until it is level with the mark on the stem of the 
pipette. Be sure to hold the mark on the pipette on a level with the 
eye so as to be able to see when the milk is on a level with the mark. 
(If a portion of the milk containing preservative should be drawn 
into the mouth, spit it out and rinse the mouth with clean water.) 
(Corrosive sublimate is very poisonous.) 

7 




Fig. 4 



The dividers in the first position 
for reading the test 



The dividers in the second position 

8 



/ 



TRANSFERRING THE MILK INTO THE TEST BOTTLES. 
First Method. — Insert the lower stem of the pipette into the 
neck of the test bottle, release the index finger and allow the milk 
to run into the bottle. (Do not lose any of the milk 
sample in the process of mixing, measuring, or trans- 
ferring, for the Babcock test is essentially a quantitative 
analysis and any loss will affect its accuracy.) (See 
Fig. 5.) 

Second Method. — Empty the sample into the test 

bottle by inserting the tip of the pipette into the mouth 

V of the test bottle, the mouth of the test bottle and the 

pipette being slanted in opposite directions, as shown in 

figure. (See Fig. 7.) 

Release the index finger and allow the milk to run 
slowly into the bottle in such a way as to permit the air 

Wto escape from the bottle without causing the milk to 
bubble out. In either case blow the last drop of milk 
out of the pipette before removing it from the test bottle. 

Adding the Acid. — Fill the acid 
measure to the mark with sulphuric 
acid testing 1.82 or 1.83 specific 
\f gravity at 60 degrees Fahr. Pour 

the acid into the test bottle, holding 
the latter in an inclined position so 
that the acid will flow down the 
sides of the test bottle and not drop 
through the body of the milk in the 
bottle, the bottle being revolved so 
as to wash down all adhering par- 
ticles of milk that may cling to the 
neck of the bottle. Charring of the 
milk and spilling of the acid will then be avoided. 
The acid will flow beneath the milk because it is 
heavier than the milk. Acid will eat holes in 
the flesh or clothing wherever spilled on them 
and should be washed off with water to which ; 

has been added ammonia water. \ / 

The acid is added to destroy all the milk 
solids except the fat. In this process great heat 
will be produced, but this is advantageous since 
the fat must be kept in a liquid condition in 
order to perform the test properly. The best 
acid is colorless and should never contain any 

9 



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["N 



Fig. 5 

Another method 
of emptying 
Pipette into 
Test Bottle 




Fig. 7 

Emptying Pipette into Test Bottles 



undissolved material, as this is likely to 
rise with the fat and affect the read- 
ing. Glass stoppers must be used in- 
stead of ordinary corks on the acid 
bottles. 

If the acid has been properly added 
there will be distinct layers of acid and 
milk in the test bottle without any 
black layer of partially mixed acid 
and milk between. 

MIXING THE ACID AND THE 
MILK. 



Mix the acid and the milk by shak- 
ing the bottle with a gentle rotary motion so that the acid will act 
equally on all parts of the milk. (See Fig. 9.) The mixture will now 
be of a dark brown color, with no undissolved particles remaining. 
It is well to mix the contents of the bottle for at least half a minute 
after all the milk has apparently been dissolved by the acid. During 
the filling and mixing, point the neck of the bottle away from the face, 
so that no drop of acid may be thrown into the eyes, as the mixing 
of the acid with the milk is often violent and may cause a drop to spurt 
out of the test bottle. 

WHIRLING IN THE CENTRIFUGAL MACHINE. 

The test bottles with the acid and milk properly mixed are now 
placed in the centrifugal machine, arranging the bottles in pairs at 
opposite sides of the center so that they will balance when rotated. 
An uneven number of bottles cannot be whirled. Whirl 5 minutes 
at the proper speed, which is as follows : 



Diam. of Tester. 
14 . . . 
16 . . . 

18 . . . 
20 . . . 



Rotations per min. 

. 875 to 925 
. 825 to 875 

. 775 to 825 
. 725 to 775 



Stop the machine and add soft water at a tem- 
perature of 170 degrees Fahr. until the fat rises to the 
neck of the bottle. All water added must be soft as 
the use of hard water may cause bubbles on the top 
of the fat column. Rewhirl at the proper speed for 2 
minutes and add soft water at a temperature of 170 

10 




Fig. 8 

Acid Measure 



degrees Fahr. until the fat column rises 
to the 6 or 7 per cent. mark. (For 8 per 
cent, bottles.) Rewhirl at the proper 
speed for one minute and temper the 
bottles. 

TEMPERING THE TESTS. 

Since butter fat expands and contracts 
rapidly with changes in temperature it is 
necessary to keep the fat column at a 
constant temperature of 120 to 140 de- 
grees Fahr. by placing them in a water 
bath of that temperature so that the water 
stands above the fat column in the necks 
of the bottles. 




Fig. 9 

Proper Motion for a Test Bottle 
while Mixing Milk and Acid 



B 



READING THE TESTS. 

Milk tests are read from the extreme bottom to the extreme top 
of the fat column. In reading the tests hold the bottle perpendicular 
and on a level with the eye. Place one point of the dividers at the 
lower end of the fat column and the other point at the top of the fat 
column. Then lower the dividers until the lower point is on the 
zero mark of the test bottle; the upper point will indicate the per 
cent, of fat. Care must be taken to hold the dividers rigid while 
lowering. (See Figs. 4 and 10.) 

COMMON CAUSES OF POOR TESTS. 

1. Insufficient mixing of milk and acid, which may cause either 
a burned test or leave some of the curd undissolved. 

2. Too much or too little acid, the former 
giving a dark fat column containing charred 
matter and the latter a very light one with some 
undissolved curd at the bottom of the fat 
column. 

3. Too strong or too weak acid, the for- 
mer leaving a dark fat column while the latter 
will give a very light colored fat and some 
undissolved curd. 

4. Too high temperature of either acid or 
milk or both. The result will always be a 
dark fat column containing charred matter. 
Try to have the acid and milk between 60 
degrees Fahr. and 70 degrees Fahr. 

5. Running the tester at too low a speed generally results in too 
low a test. 

6. Hard water, which is apt to give a white foam on top of fat 
column. 

7. Inaccuracy in reading of fat column. 

11 



Fig. 10 

Read from A to D 



APPENDIX 

CAUSES OF VARIATIONS IN THE BUTTER FAT TEST 

Chapt Ohovving I/a^iations in Composition or 



AD OUAPr C/\N 
CTNT MILK 



MILK 



85 POUNDS" 
Approximate Wcight; 




5 fTff CENT MILK 

5 fo Fat 

5 y<> Milk 5ugar 
3 i ^> Casei n 



7 ^ Ai.eot- 
73 <?. As* 




7 



65.47 % Water 
tin 



TV 



Approximate Weights 


Fat 4 


LBS 4 oz 


Milk Sugaf? A 


LBS A OZ 


Ca sein z 


LBS |0 OZ 


— Albv mi n 


\o oz 


j\ Ash 


10 OZ 


Water 72 


LBS 10 OZ 


Total 55 


LBS 






4.GS o/o /*fs*. *r •Stygi-* /* 



3?.? <#b Watt/* 




o/'o T^rMt 



3 J. S3- / OX. 

/*?/*. sr -5<yg/«/? 3 j.a*. /5 ox. 
CTAsjt//* & i.a-3. 3d ox. 

/4.JL& esA*//>s 3i oz 

A&f /O oz. 

/* ox. 



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74 z^j. aioz. 



12 



VARIATIONS OF FAT IN MILK. 

The percentage of fat in normal milk varies a great deal; however, 
the fat content very seldom falls below 2.8 per cent, or above 7.2 per 
cent. The fat content of milk from a whole herd of cows varies only 
within comparatively narrow limits during the year, seldom exceeding 
.5 or .6 of a per cent. The chief factors which may cause the fat con- 
tent to vary are : 

1. The breed. 

2. The individuality. 

3. The age. 

4. The time between milkings. 

5. The manner of milking. 

6. Whether the milk is fore or after milk. 

7. Length of time since cow has freshened. 

8. Condition of cow. 

9. Excessive heat or cold. 

10. Annoyance of flies, fleas, etc. 

11. Any harsh language or ill treatment. 

12. Chasing by dogs. 

13. Poor ventilation. 
1-1. Grooming. 

15. Shedding. 

VARIATIONS OF FAT IN MILK. 

The chief factors which may cause the fat content to vary are: 

1. Breed. The greatest difference in the test is noticed in ani- 
mals of different breeds. Jerseys and Guernseys are comparatively 
high testers, while Holsteins are low testers. 

2. The Individuality. There are undoubtedly cows of each breed 
which are much better testers than others of the same breed. Al- 
though the Holsteins as a whole are comparatively low testers, never- 
theless there are individuals of the Holstein breed which are much 
better testers than many of the Jersey breed. 

3. The Age of the Cow. Young heifers will nearly always pro- 
duce milk testing a higher per cent, of fat during their first lactation 
period than during succeeding lactation periods, other conditions, 
of course, being the same. 

13 



4. The Time Between Milkings. Usually the time between milk- 
ings varies, the longer period being between evening and morning 
milkings. On account of this difference of time as well as from other 
causes the test for the morning's milk will vary from the test for 
the evening's milk. Often the two will vary as much as .5 of a per 
cent. (Commonly called 5 points.) 

5. The Manner of Milking. Each cow should be milked by the 
same person who is acquainted with the individuality of the cow, and 
more particularly by the person with whom the cow is acquainted. 
Some cows will not tolerate a strange milker, and all will show a 
change in the butter fat test if milked under strange conditions. 

6. Whether the Milk is Fore or After Milk. The fore milk con- 
tains very little butter fat while the after milk is very rich in butter 
fat, often reaching 15 per cent. It is, therefore, very essential that 
the cow is milked clean in order to get all of the butter fat. The 
practice of letting the calf have the after milk is all right for the calf 
but hard on the butter fat test. Let the calf have the fore milk, which 
contains less butter fat. It is good dairy practice, however, to feed 
the milk while warm to the calves and not let them suck at all, 
thereby avoiding any udder trouble caused by the calf. 

7. Length of Time Since Cow Has Freshened. A cow just 
freshened has a lower butter fat test than she will have when she is 
approaching the end of her lactation period, but if a cow has been 
fattened just before calving she will give a high testing milk for 
3 or 4 weeks, when the test drops back again to normal conditions. 

8. Condition of the Cow. The nervous temperament and gen- 
eral condition of a cow will temporarily affect the butter fat test, 
particularly tending to reduce it. 

9. Excessive Heat or Cold. When the cow is annoyed by ex- 
cessive heat or shivering from the cold the butter fat is invariably 
reduced. 

10. Annoyance of Flies and Fleas. The worry and annoyance of 
flies and fleas also diminish not only the flow but the butter fat test. 

11. Harsh Language. Ill treatment of any kind causes a cow 
to become nervous and causes a reduction of the butter fat if not of 
the flow. 

12. Chasing by Dogs. It is convenient to have dogs or children 
bring the cows to the barn, but the nervous excitement through fear 
of the dogs is anything but conducive to a large flow or a maximum 
test of butter fat. 

14 



13. Poor Ventilation. Cows breathing impure air are soon af- 
fected by a general sluggish disposition. An active cow gives the 
maximum flow and test and anything which detracts from the gen- 
eral active condition of a cow reduces both flow and test. 

14. Grooming. Experiments have conclusively determined that 
a cow responds to grooming to a greater extent than any other thing. 
Just as a horse requires less feed, goes faster, and is in better con- 
dition when carefully groomed than when neglected, so a cow more 
than repays for the use of a comb and brush. It seems more than 
reasonable that a cow which is put in stanchions must be groomed, 
because she cannot groom herself as she could out in the open. 

15. Shedding. Just as a hen ceases laying eggs during her 
molting period so a cow is affected to a slight extent when she is 
shedding. Part of the energy which formerly went to milk produc- 
tion goes to hair production, and naturally a slight decrease can be 
expected. 



15 



REFERENCES 



BOOKS. 

ROSCOE H. SHAW: 

"Chemical Testing of Milk and Cream." 

VAN SLYKE : 

"Modern Methods of Testing Milk and Milk Products." 

FARRINGTON & WOLL: 

"Testing Milk and Milk Products." 

Very valuable suggestions from the following bulletins 
were freely used: 

Popular Bulletin 75 — Washington. 

Bulletin 201 — Oregon. 

Bulletin 202— Colorado. 

Bulletin 337— Cornell. 

Ext. Series Bulletin 2 — Michigan. 

Extension Bulletin 25 — Nebraska. 

Reading- Course Lesson 118 — Cornell. 



Circular 27 — Wisconsin. 

Circular 37 — Missouri. 

Circular 41 — Missouri. 

Circular 61 — Missouri. 



Circular 174 — Illinois. 

Circular 45 — Kansas. 

Circular 16 — Iowa 

Circular 41 — Indiana. 



Circular 32 — Iowa. 



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